Main work
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Convection and magnetic field generation in rotating spherical fluid shells.
Stellar and planetary magnetic fields, including the best known
geomagnetic field, are among the most notable properties of stars and
planets and play a crucial part in a variety of cosmic processes.
The established theory of the nature of these magnetic fields field is
that they are generated by a dynamo process driven by convection in
the fluid regions of planets and stars. These regions are inaccessible
for direct observations, e.g. the Earth's fluid outer core where the
geomagnetic field is generated is located at some 2800km below the
surface of the planet. Self-consistent numerical models are thus one
of the very few methods available to obtain key insights into the
convection-driven dynamo process as well as into a myriad of other
aspects of stellar and planetary structure and dynamics where many
questions still remain open.
In the last 10 years, we have developed cutting-edge numerical models
and expertise in simulation of geo- and planetary magnetic fields. We
solve the fully nonlinear magnetohydrodynamic equations, derived from
first-principles without ad-hoc turbulent and transport
models. Although restricted to moderately turbulent regimes by the
computing power available at present, this approach is desirable for
its self-consistency. By studying the parameter dependences and the
basic physical mechanisms of the convection and the dynamo processes,
we hope to achieve a meaningful extrapolation towards the turbulent
regimes of actual stellar and planetary magnetic fields.
While the state-of-the-art models still fall short of resolving the
full details of the geo-, planetary and stellar magnetic fields, it is
essential to keep building up capability in this area. For instance,
the presence of the geomagnetic field has broad implications for life
on our planet. It shields Earth's surface from harmful incoming
radiation and protects the many man-made satellites orbiting the
planet. Geomagnetism has been long used as a navigational aid by
humans and animals and has fascinated people since antiquity.
Similarly important are the studies of solar magnetism, which is so
strong that it controls much of the visible solar activity, and of
planetary magnetism, which can tell us much about the geology and the
formation of planets.
For additional details on the subject in general and on my work in particular
visit my list of publications.
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Excitation and propagation of waves in cardiac tissue and other excitable media.
Through coordinated contraction of the heart, blood is pumped to all parts of
the human body ensuring our health and vitality. This mechanical activity of
the heart is controlled by electrical impulses, called action potentials, which
propagate along the membranes of the cardiac cells. An irregular action
potential propagation leads to irregular mechanical activity of the heart. Such
conditions are known as cardiac arrhythmias. Cardiac arrhythmias are abnormal
often life-threatening events. Some of them can lead to sudden cardiac death
which is the leading cause of death in the industrialised
world. Mathematically, the normal as well as the abnormal propagation of
cardiac action potentials can be modelled by a system of partial differential
equations. Thise equations are proposed on the basis of physiological
measurements and differ for the various types of cardiac tissues. The
contemporary cardiac models are remarkably detailed and provide impressive
accuracy. They are very complicated and consist of a large number of equation
and thus by necessity they have to be solved numerically. However,
simplifications of the detailed cardiac models exist. Such simplifications can
be achieved by taking into account the asymptotic structure of the detailed
models.
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for a more mathematical description..
For additional details on the subject in general and on my work in particular
visit my list of publications.
General interests
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Non-linear Dynamical Systems.
Non-linear partial differential equations are central
to mathematics, pure and applied. They provide an universal
approach to describing almost any physical system which depends on
continuously varying independent variables. Their relevance is
growing, powered by modern computational equipment,
capable of solving suitably discretized approximations of the
equations. Equally important is the impact the non-linear partial
differential equations
have on fundamental mathematics, opening new branches,
cross-fertilising existing ones, benefiting from the results. In
addition to numerical methods, I am also interested in algebraic,
topological, and group methods in the theory of dynamical
systems.
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Applications of Differential Equations to Physical Systems.
Perturbation methods; Instability of fluid
flow and in magnetohydrodynamics; Pattern formation out of statistical equilibrium;
Rotating thermal convection; Dynamo theory; Geophysical fluid
dynamics; Cardiac modelling.
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Recreational & Technical.
Algorithms; Programming techniques, languages and
tools; Computer Algebra Systems; Visualization.
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